Some semiconductor devices are designed to detect deformation of a strain-causing body, such as a diaphragm, by bonding a semiconductor chip having sensor functions to the strain-causing body. Strain-causing bodies are often formed of metal such as stainless steel (SUS). In such a semiconductor device, the semiconductor chip may be detached or destroyed due to the differences in thermal expansion coefficient between the strain-causing body and a bonding agent and between the semiconductor chip and the bonding agent. For this reason, a known pressure sensor uses a bonding agent whose thermal expansion coefficient changes in a continuous manner from the side of semiconductor chip to the side of the strain-causing body. The thermal expansion coefficient of the bonding agent is adjusted by changing the amount of a silica filler added to its main component, or glass (see, for example, Patent Document 1).